Common Conditional Statements in Revit

BIM Software Tip: Common Conditional Statements in Revit

1) Selecting between two parameters based on one parameter:

L = if(a > 3000mm, 5000mm, 7500mm)

Explanation: If a is greater than 3000mm, then L is 5000mm; otherwise, L is 7500mm.

2) Choosing between two parameters based on whether one parameter is true:

L = if(a, 5000mm, 7500mm)

Explanation: If a evaluates to “True,” then L is 5000mm; otherwise, L is 7500mm.

For example, if a = 3 > 2, then L = 5000mm.

3) Dividing another parameter into three segments based on two conditions:

Rotation angle = if(d < 34000 mm, a1 * n, if(d < 94000 mm, 10 * a1 * (n - 10) * a2, 10 * a1 * 20 * a2 * (n - 30) * a3))

Explanation: When d is less than 34 meters, the rotation angle is a1 * n. If d is between 34 meters and 94 meters, it becomes 10 * a1 * (n - 10) * a2. If d exceeds 94 meters, the rotation angle is 10 * a1 * 20 * a2 * (n - 30) * a3.

4) Conditional visibility constraints:

V = a > b

Explanation: When a is greater than b, the condition is met, making the element visible (checked). Otherwise, the element remains hidden (unchecked).

Additional Geometric and Mathematical Formulas:

Circle and Triangle Calculations:

S = abc / 4R — where R is the radius of the circumscribed circle; this formula relates the radius to the triangle’s sides and area.

5) Calculating arc length given a central angle an:

= 2 * pi() * r * (an / 360°)

6) Calculating the central angle given three sides and radius:

= 2 * asin(0.5 * c / r) — calculates angle C based on side length c.

7) Radius of an inscribed circle:

= 2 * s / (a + b + c)

Explanation: The area S of the triangle is equal to the sum of the areas of three smaller triangles, which is (r / 2) * (a + b + c) = S.

8) Calculating the volume of a triangular pyramid given angles and side edges:

= (1/6) * a * b * c * sqrt(1 + 2 * cosA * cosB * cosC - cosA^2 - cosB^2 - cosC^2)

9) Calculating the volume of a triangular pyramid given the base area and height:

= (1/3) * S * h

10) Finding the height given the volume and base area of a triangular pyramid:

h = 3 * V / S

11) Triangle area formula given three sides (Heron’s formula):

S = sqrt[p(p - a)(p - b)(p - c)]

or

= (1/4) * sqrt[(a + b + c)(a + b - c)(a + c - b)(b + c - a)]

Example in Revit expressions:

= 0.25 * sqrt((a + b + c) * (a + b - c) * (a + c - b) * (b + c - a))

= 0.25 * sqrt((d + e + f) * (d + e - f) * (d + f - e) * (f + e - d)) — for a second triangle.

12) Cosine law:

cosA = (b² + c² - a²) / (2 * b * c)

In Revit expression form:

= acos((b^2 + c^2 - a^2) / (2 * b * c)) — calculates angle A using inverse cosine.

Similarly, for angle B:

cosB = (a² + c² - b²) / (2 * a * c)

Calculate sinB given cosB:

sinB = sqrt(1 - cosB^2)

13) Triangle area formula given two sides and the included angle:

S = 0.5 * a * b * sinC

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